The present invention relates to a unit for conveying products.
In particular, the present invention relates to a unit for conveying products to a user machine, and more exactly a unit comprising a first and a second conveyor set in continuous motion.
The invention finds application, to advantage, in the art field of conveying systems for packets of cigarettes, to which reference is made explicitly in the specification albeit implying no limitation in scope.
In a typical cigarette packaging line, packets turned out by a cigarette packer are directed into a cellophaner, which proceeds to envelop each one in an overwrapping of polypropylene; the packets are supplied to the cellophaner by a first conveyor carrying the main flow from the packer, randomly spaced, and by a second recycle conveyor or hopper, which carries unblemished packets readmitted to the production cycle upstream of the cellophaner.
The readmission step is made necessary for one reason more than any other, namely that to operate correctly, the user machine must be supplied with packets in a continuous and ordered succession, whereas in practice it can happen that gaps will appear in the flow of packets proceeding toward the cellophaner, and in consequence empty spaces on the conveyor, attributable to various different causes.
Owing to constraints determining the way that the outfeed conveyor of the cigarette packer and the infeed conveyor of the cellophaner are positioned in space, the path followed by the aforementioned first or main conveyor will generally incorporate 90° and 180° bends and changes of level, and it is therefore normal for the conveying path to include curvilinear stretches along which the packets are directed downwards toward the cellophaner. These non-rectilinear stretches of the conveying path can cause damage to packets propelled forward at the high operating speeds of modern cigarette packers. In effect, the packets advance broadside along the rectilinear sections of the path, proceeding in close order with one larger side face resting on the belt of the conveyor, and are caused to strike one against another when passing through the bends and down the gradients of the path. In particular, it will often happen that the corner of one packet rubs against the flank face of the packet in front, generating wear.
A further problem connected with random spacing of the packets is that the dynamic by which they are carried along the path cannot be controlled, so that it is not possible to apply additional items to the packets, such as coupons and/or leaflets, before their entry into the cellophaner.
Positioned generally alongside the main conveyor, the recycle hopper containing readmissible packets is associated with a push rod designed to eject the lowest packet from the hopper and direct it onto the main conveyor whenever there is a gap in the flow of packets advancing on the selfsame conveyor.
More particularly, given that the packets do not advance in a regularly spaced succession, it is not possible with this type of feed system to predict when there are going to be gaps on the conveyor, and the recycle hopper comes into operation only when the cigarette packer is at standstill. Even with the recycle hopper installed and in operation, consequently, there will always be unpredictable gaps in the flow of packets directed along the main conveyor toward the cellophaner, and the resulting empty spaces reduce the efficiency of the machine considerably.
Attempts have been made to avoid damage to the packets along the non-rectilinear stretches of the main conveyor, by employing conveyors on which the selfsame packets are fed to the cellophaner in a regularly spaced succession, each one occupying a stable position determined by a relative projection or ridge on the surface on the conveyor.
A solution of this type precludes the use of the conventional recycle hopper to readmit unblemished packets as described above, since, at the high operating speeds of the user machine, the cycle time needed for a push rod to transfer a packet from the hopper to the main conveyor would be much longer than the time taken by the empty space to pass across the outlet of the selfsame hopper.
Solutions of other types would be notably complex from the constructional standpoint, inasmuch as they would be based on the use of a hopper capable of traversing parallel with the feed direction of the flow of packets and thus allowing the outlet to track the adjacent gap so that a recycled packet can be placed accurately in the required position.
The object of the present invention is to provide a conveying unit for products, presenting a first conveyor and a second conveyor feeding respective ordered flows of the products, such as will allow products missing from the first ordered flow to be made up with products from the second ordered flow, even at the high operating speeds of user machines, employing a device of simple and practical design.
Adopting a unit in accordance with the invention, in particular, any packets missing from the first ordered flow can be made up as the selfsame flow advances, without its progress being interrupted.